De Santiago Alejandro, Barnes Shelby, Pereira Tiago José, Marcellino-Barros Mirayana, Durden Lekeah, Han Min Khant, Thrash J Cameron, Bik Holly M
Institute of Bioinformatics, University of Georgia, Athens GA 30605.
Department of Marine Sciences, University of Georgia, Athens, GA 30605.
bioRxiv. 2025 Aug 22:2025.08.22.671635. doi: 10.1101/2025.08.22.671635.
Despite growing insights into the composition of marine invertebrate microbiomes, our understanding of their ecological and evolutionary patterns remains poor, owing to limited sampling depth and low-resolution datasets. Previous studies have provided mixed results when evaluating patterns of phylosymbiosis between marine invertebrates and marine bacteria. Here, we investigated potential animal-microbe symbioses in , an overlooked bacterial genus consistently identified as a core microbiome taxon in diverse invertebrates. Using a pangenomic analysis of 236 free-living and invertebrate-associated bacterial strains (including two new nematode-associated isolates generated in this study), we confirm that is a novel symbiont with substantial evidence of phylosymbiosis across at least three marine invertebrate phyla (e.g., Nematoda, Mollusca, and Cnidaria). Patterns of symbiosis were consistent irrespective of geography (including in Antarctica), with FISH images from nematodes indicating that bacterial symbionts form biofilms in the mouth and esophagus. The evolutionary history of is marked by substantial host-switching and lifestyle transitions, and host-associated genomes suggest that these bacteria are facultative symbionts involved in nutritional mutualisms. In marine environments, we hypothesize that horizontally-acquired symbionts may have co-evolved with invertebrates, using host mucus as a physical niche and food source, while providing their animal hosts with Vitamin B, amino acids, and bioavailable carbon compounds in return.
尽管对海洋无脊椎动物微生物组的组成有了越来越多的认识，但由于采样深度有限和数据集分辨率低，我们对其生态和进化模式的了解仍然很少。以前的研究在评估海洋无脊椎动物和海洋细菌之间的系统共生模式时得出了不一致的结果。在这里，我们研究了 中的潜在动物-微生物共生关系，这是一个被忽视的细菌属，一直被认为是多种无脊椎动物核心微生物组分类群。通过对236个自由生活和与无脊椎动物相关的细菌菌株（包括本研究中产生的两个新的与线虫相关的分离株）进行泛基因组分析，我们证实 是一种新型共生体，有充分证据表明其在至少三个海洋无脊椎动物门（如线虫门、软体动物门和刺胞动物门）中存在系统共生。无论地理位置如何（包括南极洲），共生模式都是一致的，来自线虫的荧光原位杂交图像表明细菌共生体在口腔和食道中形成生物膜。 的进化历史以大量的宿主转换和生活方式转变为特征，与宿主相关基因组表明这些细菌是参与营养互利共生的兼性共生体。在海洋环境中，我们假设水平获得的共生体可能与无脊椎动物共同进化，将宿主黏液作为物理生态位和食物来源，同时为其动物宿主提供维生素B、氨基酸和生物可利用的碳化合物作为回报。
